Angela Merkel’s seemingly unassailable lead in the German election campaign faces an unpredictable threat from the country’s first mainstream eurosceptic party.

The German Chancellor’s Christian Democrats this month recorded their highest levels of support — 41 per cent — since Mrs Merkel was re-elected in 2009, with the main opposition Social Democratic Party on only 27 per cent.

But polls suggested that some CDU voters could be tempted to switch to Alternative for Germany (AFD), an anti-euro party being launched nationally next weekend. Seven per cent of voters said that they could imagine voting for the new party and a further 17